(1) Field of the Invention
The present invention pertains to a microsurgical laser probe used primarily in ophthalmic surgery. The probe has a handle and a tubular sleeve and a distal end portion of an optic fiber projecting from the sleeve can be caused to bend relative to the sleeve by manual manipulation of a mechanism on the probe handle.
(2) Description of the Prior Art
In ophthalmic surgery, various different types of instruments are available for use by the surgeon to transmit laser energy to a surgical site in the interior of the eye. The typical microsurgical laser probe comprises a handle with a small cylindrical metal sleeve projecting from a distal end of the handle. An optic fiber, having a proximal end with a connector for coupling to a source of laser light, passes through the center of the handle and the sleeve of the probe. The distal end of the optic fiber is positioned adjacent the distal end of the sleeve. In instruments of this type, the sleeve can project straight from the handle of the instrument or can have a slight bend or curve as it projects from the instrument handle.
Efficient delivery of laser light in the eye interior toward the anterior or front portion of the retina is often awkward to the surgeon using a straight laser probe. This is due to the positioning of the incision or instrument entry site in the eye relative to the target area or surgical site of the laser light being transmitted. This is illustrated in FIG. 1 where an area A of the eye interior is inaccessible to the straight tip of the laser probe shown. The use of curved laser probes such as that shown in FIG. 2 allows for a greater range of coverage inside the eye, thereby minimizing the risk of hitting the lens of the eye with the laser light and overcoming the disadvantages of the straight sleeve laser probe discussed above. However, curved laser probes cannot be inserted through straight cannulas and therefore must be directed through the eye incision site itself.
The optimal deliver of laser light to a surgical site in the eye requires that the laser be directed perpendicular to the target area of the surgical site. Directing a straight laser probe at anterior or forward portions of the retina causes the approach angle, or angle of incidence of the laser light, to be large. In this situation the optimal delivery of laser light to the surgical site cannot be achieved. Additionally, torquing or manipulating the tubular sleeve of the straight probe in the entry incision to reduce the angle of approach of the laser light to the surgical site in these awkward areas often produces excessive, and sometimes harmful stresses around the incision of the eye. Often the only way for the surgeon to overcome this situation is to create a second incision site for insertion of the laser probe. These problems can be overcome by using a curved laser probe that can effectively eliminate the use of a secondary incision site since an increased area in the eye interior is accessible from the single entry site as illustrated in FIG. 2. Currently available curved laser probes are able to access more anterior or forward areas of the eye interior than can be achieved with straight laser probes. However, because their curvatures are fixed, curved laser probes are not efficient at directing laser energy to areas even more anterior or more forward in the eye that would require a tighter bend or curvature of the probe sleeve, or areas at the far end or posterior of the retina which would require a straight sleeve laser probe due to the approach angle.
To overcome these disadvantages of prior art straight and curved laser probes, what is needed is an adjustable directional laser probe that is capable of reducing the approach angle or angle of incidence of light toward the surgical site, thereby providing ease of access and reduced instrument manipulation at the target site, reduced tissue stress at the point of entry, and improved laser focusing by directing the laser energy more perpendicular to the target surgical site.
The directional laser probe of the present invention may be constructed having either a disposable hand piece or a reusable hand piece and, although described as transmitting laser light, it may also be employed in transmitting light for illumination. The directional laser probe makes use of a shape memory metal alloy, nitinol, to steer and direct a flexible optic fiber to a surgical target site. Alternative shape memory materials such as spring steel or plastics may also be used. Whether the target site lies in the posterior or anterior portions of the eye interior, the directional laser probe can easily deflect to any angle between 0xc2x0 (or a straight configuration) and 90xc2x0 or more. The flexible nature of the nitinol alloy allows variable adjustment of the bend angle of the probe to deliver laser energy to the target site. Additionally, cannulas may be used in the incision site of the eye because the laser probe, when in its straight configuration, can be inserted through the cannula to position the tip of the probe in the interior of the eye, and then a bend can be created at the tip of the probe in the eye interior. The directional laser probe is especially useful when accessing anterior portions of the retina, or areas that are difficult or awkward to access using traditional straight probes.
The directional laser probe of the invention is basically comprised of a handle having an interior bore passing through its center and having a recess formed in a side of the handle communicating with the interior bore. A tubular sleeve projects from a distal end of the handle and is received in the bore for axial sliding movement relative to the handle. A finger pad positioned in the recess is connected to the sleeve and manipulating the finger pad axially through the recess causes the sleeve to be moved between a pushed forward position where it projects its greatest distance from the distal end of the handle, and a pulled back position where the sleeve projects its shortest distance from the distal end of the handle. A tubular nitinol tip passes through the sleeve and is secured stationary relative to the handle. A length of optic fiber enters the handle bore at the handle proximal end and a distal end portion of the optic fiber passes through the bore and the nitinol tip. The proximal end of the fiber is connected to a standard light source connector, for example a SMA type connector.
The nitinol tip that passes through the sleeve is annealed in a pre-bent 90xc2x0 bend in its preferred embodiment. When the finger pad of the instrument is pushed forward, it extends the sleeve to its pushed forward position in which the nitinol tip and the distal end portion of the optic fiber are completely contained inside the tubular sleeve. When the finger pad is moved to its pulled back position, the sleeve is also moved back to its pulled back position causing the bent portion of the nitinol tip and the distal end portion of the optic fiber to be gradually exposed at the distal end of the sleeve. As the nitinol tip and the optic fiber contained therein are exposed at the end of the sleeve, they gradually bend from the initial straight configuration of the sleeve toward the 90xc2x0 pre-bent configuration of the nitinol tip. In this manner, the optic fiber contained in the nitinol tip can be adjustably positioned through any angle between 0xc2x0 when the nitinol tip and optic fiber are entirely contained in the tubular sleeve at its pushed forward position, to a 90xc2x0 bend when the nitinol tip and optic fiber project from the sleeve distal end with the sleeve moved to its pulled back position.
In use of the directional laser probe, the optic fiber connector is first attached to a laser power source. With the finger pad in its pushed forward position, the optic fiber is contained in the sleeve which projects in a straight line from the distal end of the handle. The sleeve is then inserted through a cannula positioned in an incision in the eye or inserted directly through the incision, positioning the sleeve in the eye interior. The finger pad is then slowly moved toward the rear of the handle causing the sleeve to slowly move toward its pulled back position relative to the handle. This, in turn, causes the distal end portion of the optic fiber contained in the pre-bent portion of the tubular nitinol tip to gradually bend from its straight configuration toward its 90xc2x0 configuration. The bending of the fiber allows optimal positioning of the fiber tip to areas where a straight fiber may not reach. Rotation of the entire instrument about its center axis may be necessary to further direct the optic fiber tip. Once the proper location of the fiber tip is achieved, laser energy can then be delivered to the site of interest. Retraction of the fiber tip into the sleeve is performed by first pushing the finger pad forward, causing the sleeve to move toward its pushed forward position and causing straightening of the bent portion of the optic fiber projecting from the sleeve. With the optic fiber contained in the sleeve, the sleeve is then pulled back through the surgical entry site.